The present invention relates to a manufacturing method of a thin-film magnetic head with a magnetoresistive effect (MR) element for detecting magnetic intensity in a magnetic recording medium and for outputting a read signal.
Recently, in order to satisfy the demand for higher recording density and downsizing in a hard disk drive (HDD) apparatus, higher sensitivity and larger output of a thin-film magnetic head are required. Thus, improvement in characteristics of a general giant magnetoresistive effect (GMR) head with a GMR element which is current-manufactured are now strenuously proceeding and also development of a tunnel magnetoresistive effect (TMR) head with a TMR element is energetically performed.
Because of the difference in flowing directions of their sense currents, structures of these TMR head and general GMR head differ from each other. One head structure in which a sense current flows in a direction parallel with surfaces of laminated layers as in the general GMR head is called as a current in plane (CIP) structure, whereas the other head structure in which a sense current flows in a direction perpendicular to surfaces of laminated layers as in the TMR head is called as a current perpendicular to plane (CPP) structure.
In recent years, CPP-GMR heads not CIP-GMR heads are being developed. For example, Japanese patent publication No. 05275769A discloses such a CPP-GMR head. Japanese patent publication Nos. 04360009A, 05090026A and 09129445A disclose CPP-GMR heads having anti-ferromagnetic coupling magnetic multi-layered films consisting of a plurality of magnetic layers stuck with each other via nonmagnetic layers (Cu, Ag, Au or others).
Also, provided are CPP-GMR heads with spin valve magnetic multi-layered films including such as specular type magnetic multi-layered films or dual-spin valve type magnetic multi-layered films.
Conventionally a lift-off method or a contact-hole method has been used for fabricating such CPP-GMR heads or TMR heads.
FIGS. 1a to 1f show sectional views illustrating a part of a conventional fabrication process of a CPP-GMR head by the lift-off method.
First, as shown in FIG. 1a, a lower electrode film 11 and a MR multi-layered film 12xe2x80x2 are sequentially deposited on an insulation film 10 formed on a substrate (not shown).
Then, a photo-resist pattern 13 of a two-layers structure is formed thereon as shown in FIG. 1b, and the MR multi-layered film 12xe2x80x2 is patterned by ion milling to obtain a MR multi-layered structure 12 as shown in FIG. 1c. 
Then, an insulation film 14xe2x80x2 is deposited thereon as shown in FIG. 1d, and the photo-resist pattern 13 is removed or lifted off to obtain a patterned insulation film 14 as shown in FIG. 1e. 
Thereafter, an upper electrode film 15 is deposited thereon as shown in FIG. 1f. 
In executing this lift-off method, it is necessary that no insulation film 14xe2x80x2 deposited on the side surface of a stepped portion of the photo-resist pattern 13 is bridged over the stepped portion. Thus, in general, a T-shaped two-layers structure photo-resist pattern with an undercut is used in order to improve the lift-off performance.
However, if the amount or depth of the undercut of the photo-resist pattern 13 is small, the insulation film may be deposited on a side surface of a base 13a of the two-layers structure photo-resist pattern 13 causing occurrence of unnecessary burr around the removed photo-resist pattern. Contrary to this, if the undercut amount is large, a burr will be prevented from occurrence but the width of the base 13a of the photo-resist pattern 13 will become extremely narrow causing lost of the pattern.
Also, according to the lift-off method, a part of the insulation film 14 intruded into the undercut portion may be remained to overlap with a top surface of the MR multi-layered structure 12 as shown in FIG. 1e. Such overlapped insulation film causes ambiguity in a track width and limits fine micromachining of the track width. Since the length of each overlapped insulation film on the MR multi-layered structure is about 100 nm, it is impossible to fabricate by the lift-off method a recent TMR element or GMR element with an extremely narrow track width of 200 nm or less, such as around 100 nm.
In typical MR multi-layered structure of the TMR or GMR element, a free layer is located at a middle of the MR multi-layered structure and its width determines the track width. Therefore, if the MR multi-layered structure is formed by ion milling using the conventional photo-resist mask, the bottom of the MR multi-layered structure will widen causing an effective track width to increase. It is desired that the side surface of the MR multi-layered structure is perpendicular to the substrate surface and this may be implemented by an ion milling method using a hard mask or by a reactive ion etching (RIE) method. However, in principal, such methods cannot be utilized in the lift-off method.
FIGS. 2a to 2g show sectional views illustrating a part of a conventional fabrication process of a CPP-GMR head by the contact-hole method.
First, as shown in FIG. 2a, a lower electrode film 21 and a MR multi-layered film 22xe2x80x2 are sequentially deposited on an insulation film 20 formed on a substrate (not shown).
Then, a photo-resist pattern 23 is formed thereon as shown in FIG. 2b, and the MR multi-layered film 22xe2x80x2 is patterned by ion milling to obtain a MR multi-layered structure 22 as shown in FIG. 2c. 
Then, after the photo-resist pattern 23 is removed, an insulation film 24xe2x80x2 is deposited thereon as shown in FIG. 2d. 
Then, as shown in FIG. 2e, a photo-resist pattern 26 with an opening 26a located at a contact hole is formed on the insulation film 24xe2x80x2.
Then, as shown in FIG. 2f, the insulation film 24xe2x80x2 is patterned by ion milling to obtain an insulation film 24 provided with a contact hole 24a on the MR multi-layered structure 22, and thereafter the photo-resist pattern 26 is removed.
After that, an upper electrode film 25 is deposited thereon as shown in FIG. 2g. 
According to this contact-hole method, however, since two photo processes with respect to the photo-resist patterns are executed, the amount of the overlap due to a deviation between both the alignments will become about 30 nm. Such overlap amount of the insulation film cannot be negligible as well as in case of the lift-off method.
As aforementioned, according to the conventional manufacturing method, it is quite difficult to fabricate a GMR head with the CPP structure or a TMR head having a very narrow track width of 200 nm or less, and therefore it has been demanded to provide a novel fabrication method capable of fabricating such CPP-GMR head or TMR head with the extremely narrow track width.
It is therefore an object of the present invention to provide a manufacturing method of a thin-film magnetic head with an MR element, whereby an MR element with a structure in which a sense current flows in a direction perpendicular to surfaces of laminated layers and with a track width of 200 nm or less can be easily manufactured.
According to the present invention, a manufacturing method of a thin-film magnetic head provided with an MR element includes a step of forming an MR multi-layered structure in which a current flows in a direction perpendicular to surfaces of layers of the MR multi-layered structure, on a lower electrode film, a step of depositing an insulation film on the formed MR multi-layered structure and the lower electrode film, a step of flattening the deposited insulation film until at least upper surface of the MR multi-layered structure is exposed, and a step of forming an upper electrode film on the flattened insulation film and the MR multi-layered structure.
Without using a lift-off method, an insulation film is deposited on the MR multi-layered structure and the lower electrode film, and then this insulation film is flattened until at least the upper surface of the MR multi-layered structure is exposed or appeared to form a flattened insulation film on and around the MR multi-layered structure.
Since a normal resist pattern or a hard mask with a straightly shaped side surface but no inversely tapered side surface can be used according to this method, more a finely micromachined MR multi-layered structure than that fabricated by using the lift-off method can be formed.
Also, since an RIE method or a hard mask that will prevent widening of the bottom of the MR multi-layered structure can be utilized for milling the MR multi-layered structure, a very precise shape of the MR multi-layered structure can be expected.
Furthermore, because no burr nor overlap of the insulation film will occur and thus a very strict track width can be defined, it is possible to easily fabricate an MR element with a structure in which a sense current flows in a direction perpendicular to surfaces of laminated layers and with an extremely narrow track width of 200 nm or less.
It is preferred that the forming step of the MR multi-layered structure includes depositing a MR multi-layered film on the lower electrode film, forming a mask on the deposited MR multi-layered film, patterning the deposited MR multi-layered film using the formed mask, and removing the mask to form the MR multi-layered structure.
It is also preferred that the forming step of the MR multi-layered structure includes depositing a MR multi-layered film on the lower electrode film, forming a mask on the deposited MR multi-layered film, and patterning the deposited MR multi-layered film using the formed mask to form the MR multi-layered structure, the mask being remained to use as a cap layer of the MR multi-layered structure.
It is further preferred that the flattening step includes executing a low angle ion beam etching (IBE) that uses a beam having a low incident angle with surfaces of laminated films.
Also, it is preferred that the flattening step includes executing a low angle IBE that uses a beam having a low incident angle with surfaces of laminated films, and executing a low rate IBE with a low etching rate.
It is further preferred that the flattening step includes executing a low angle IBE that uses a beam having a low incident angle with surfaces of laminated films, executing a flattening process using gas clusters ion beam (GCIB), and executing a low rate IBE with a low etching rate.
It is preferred that the low incident angle in the IBE is 0 to 40 degrees.
It is also preferred that the flattening step includes executing a flattening process using GCIB, and executing a low rate IBE with a low etching rate.
It is further preferred that the flattening step includes executing a chemical mechanical polishing (CMP). In this case, preferably the method further includes a step of forming a contact hole on the insulation film on the MR multi-layered structure before executing the flattening step.
It is preferred that termination of the flattening step is managed by monitoring a flattening step time or by executing endpoint detection. The endpoint detection may be executed by using a secondary ion mass spectroscopy (SIMS).
It is also preferred that the MR multi-layered structure is a TMR multi-layered structure, a CPP-GMR multi-layered structure, a TMR multi-layered structure with a bias layer for defining a magnetization direction of a free layer in the TMR multi-layered structure, or a CPP-GMR multi-layered structure with a bias layer for defining a magnetization direction of a free layer in the CPP-GMR multi-layered structure.
According to the present invention, also, a manufacturing method of a thin-film magnetic head provided with a MR element includes a step of forming an MR multi-layered structure in which a current flows in a direction perpendicular to surfaces of layers of the MR multi-layered structure, on a lower electrode film, a step of depositing an insulation film on a cover film formed on an upper surface of the formed MR multi-layered structure and the lower electrode film, a step of removing the deposited insulation film on the cover film formed on the MR multi-layered structure until the cover film is exposed or before the cover film is exposed by executing CMP, and a step of forming an upper electrode film on the cover film or the MR multi-layered structure and the insulation film.
Without using a lift-off method, an insulation film is deposited on the MR multi-layered structure and the lower electrode film, and then this insulation film is removed by CMP until or before a cover film on the upper surface of the MR multi-layered structure is exposed or appeared to form an insulation film on and around the MR multi-layered structure.
Since a normal resist pattern or a hard mask with a straightly shaped side surface but no inversely tapered side surface can be used according to this method, more a finely micromachined MR multi-layered structure than that fabricated by using the lift-off method can be formed.
Also, since an RIE method or a hard mask that will prevent widening of the bottom of the MR multi-layered structure can be utilized for milling the MR multi-layered structure, a very precise shape of the MR multi-layered structure can be expected.
Furthermore, because no burr nor overlap of the insulation film will occur and thus a very strict track width can be defined, it is possible to easily fabricate an MR element with a structure in which a sense current flows in a direction perpendicular to surfaces of laminated layers and with an extremely narrow track width of 200 nm or less.
In addition, when the insulation film is deposited, a recess may be produced around the MR multi-layered structure. Thus, a part of the deposited upper electrode film will enter the recess and a magnetic field passing through this electrode film part will be applied to the MR multi-layered structure causing its MR characteristics to deteriorate. However, according to the present invention, since the recess is removed by CMP, it is possible to improve MR characteristics.
It is preferred that the forming step of the MR multi-layered structure includes depositing a MR multi-layered film on the lower electrode film, forming a mask on the deposited MR multi-layered film, and patterning the deposited MR multi-layered film using the formed mask to form the MR multi-layered structure.
It is also preferred that the cover film is the formed mask. In this case, the removing step includes removing the deposited insulation film on the mask formed on the MR multi-layered structure until a part of the mask is removed by executing the CMP, and removing remained part of the mask is removed after the CMP.
It is further preferred that the forming step of the MR multi-layered structure includes depositing sequentially a MR multi-layered film and a first CMP stop film on the lower electrode film, forming a mask on the deposited first CMP stop film, and patterning the deposited first CMP stop film and the deposited MR multi-layered film using the formed mask to form the MR multi-layered structure.
It is preferred that the cover film is the first CMP stop film.
It is also preferred that the method further includes a step of depositing a second CMP stop film on the deposited insulation film.
It is further preferred that the removing step includes removing the deposited insulation film on the first CMP stop film formed on the MR multi-layered structure until the first CMP stop film is exposed by executing the CMP.
It is more preferred that the method further includes a step of removing the first and second CMP stop films after the CMP.
It is further preferred that the forming step of the MR multi-layered structure includes depositing sequentially a MR multi-layered film and a milling stop film on the lower electrode film, forming a mask on the deposited milling stop film, and patterning the deposited milling stop film and the deposited MR multi-layered film using the formed mask to form the MR multi-layered structure.
Preferably, the cover film is the milling stop film.
It is preferred that the removing step includes removing the deposited insulation film on the milling stop film formed on the MR multi-layered structure before the milling stop film is exposed by executing the CMP.
It is further preferred that the method further includes a step of removing the insulation film on the milling stop film by milling after the CMP, the milling stop film being remained.
Preferably, the CMP is a precise CMP with a low lapping rate for remaining a low height difference. A lapping rate of the precise CMP is preferably 50 nm/min or less.
It is preferred that the precise CMP is executed using a slurry consisting of one of colloidal silica, cerium oxide, corundum, boron nitride, diamond, chromium oxide, iron oxide, fumed silica, alumina and zeolite, or of a mixture containing one of colloidal silica, cerium oxide, corundum, boron nitride, diamond, chromium oxide, iron oxide, fumed silica, alumina and zeolite.
It is further preferred that the precise CMP is executed using a slurry with an average particle diameter of 100 nm or less.
It is also preferred that termination of the CMP is managed by monitoring a polishing process time.
It is further preferred that the MR multi-layered structure is a tunnel MR multi-layered structure or a CPP-GMR multi-layered structure.
Further objects and advantages of the present invention will be apparent from the following description of preferred embodiments of the invention as illustrated in the accompanying drawings.